Dissertation defence (Food Development): M. Tech Amruta Kulkarni

M.Tech Amruta Kulkarni defends the dissertation in Food Development entitled “Effect of omega-3 deficiency and positional distribution of docosahexaenoic acid in triacylglycerols on tissue lipids in rats” at the University of Turku on 5 October 2023 at 12.00 (University of Turku, Main building, Tauno Nurmela lecture hall, Turku).

Opponent: Professor Bente Ruyter (Norwegian University of Life Sciences, Norway)
Custos: Professor Kaisa Linderborg (University of Turku)


Summary of the Doctoral Dissertation:

Long-chain omega-3 polyunsaturated fatty acids are highly unsaturated fatty acids that are particularly abundant in fish and other seafood. Of the long chain omega-3 polyunsaturated fatty acids, docosahexaenoic acid (DHA) is essential for numerous biological functions such as the proper functioning of the eyes and brain and the prevention of cardiac and circulatory disorders.

In diet, fatty acids, including DHA, are present mainly as part of triacylglycerols (TAGs). TAGs contain three fatty acids that are located in three different positions on the glycerol backbone. Once TAGs are ingested, lipases in our digestive system cleave fatty acids from the TAGs to increase the solubilization. The enzymes have different specificities for different fatty acids and locations in TAGs. The fatty acids from the outer positions are cleaved off more easily compared to the fatty acid in the middle position. However, the difference between the absorption of the two outer positions has not been studied before.

To answer this question, structured TAGs containing DHA at three different positions on the glycerol backbone were synthesized and an animal feeding trial was conducted. This study investigated the effect of TAG structure on the extent of accumulation of DHA in rat brain, liver, testicle, eye, visceral fat, kidney, plasma, and feces, as well as on body weight, and organ weight.

The study showed the superior bioavailability of DHA from the middle position compared with the two outer positions as measured by the amount of DHA lost to feces. The DHA levels in the TAG-rich fraction of the liver showed a minor yet significant difference between the two outer positions. We also determined the effect of mild (n-3) deficiency on the fatty acid composition of the organs by assessing the extent of DHA accumulation in the rat organs. The results showed that the DHA content of visceral fat of the (n-3) deficient group was most affected by the (n-3) deficient diet feeding, as the brain was least affected.

Together, this work provided a comprehensive view of the effect of the positional distribution of DHA in dietary TAGs on the absorption, excretion, and accumulation, in different organs and the (n-3) deficiency on the bioavailability of DHA strengthening the current understanding of lipid biochemistry.
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